Supplementary Oil And Natural Gas Disclosures (Unaudited) (Results Of Operations For Oil And Gas Producing Activities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Sales	$ 30,245	$ 77,845	$ 47,050
Production costs	15,466	13,529	9,876
Depreciation, depletion and amortization	37,623	38,768	12,032
Reduction in value of assets	56,000
Income before income taxes	(78,844)	25,548	25,142
Income tax expenses	(28,778)	9,325	8,800
Results of operations from producing activities (excluding corporate overhead)	$ (50,066)	$ 16,223	$ 16,342